Ever wondered why stepping on a rusty nail is so dangerous? In TED-Ed’s latest video, they explore the story of a 5th-century ship master who suffered from a bizarre and terrifying infection that caused his jaws to clamp shut and his muscles to spasm uncontrollably. Today, we know this as one of the earliest recorded cases of tetanus. Discover how a toxin-producing bacterium is behind this condition, and learn about the symptoms and prevention methods that can keep you safe!